This is primarily a methodological study of infant social behavior at one year. Measures of infant behavior in several situations and several settings were made. We are studying the relationships among these measures in order to address the conceptual issue of what are the most appropriate behavioral measures of mother-infant attachment. As part of this effort we are also studying reactions to strangers. In addition to the methodological question we plan to examine the antecedents of the distinctive tie between mother and infant. Approximately half the sample was observed at six months as part of Project Z01.HD0002.04. Several of the environmental variables observed at that time have been hypothesized to relate to later attachment, e.g., amount of kinesthetic stimulation and mother's responsiveness to baby's distress.